PNG images not showing up in IE5

The situation I have is a program generates a plot of real time data and generates a png file to be displayed in IE or Mozilla etc. The image is fine in Mozilla and "broken" in IE. We have traced, we think, the problem to the filesize of the png image. Certain filesizes end up broken ONLY in IE.

One of my collegues "found" a reference to a IE patch that would fix this, but was never able to locate it or any other references to it.

If anybody has similiar experiences or other understanding, that would be EXCELLENT.